The present disclosure relates to a display panel with a touch detection function which detects a touch event by an external proximity object, and a method of driving the same, a drive circuit, as well as an electronic unit having such a display panel with a touch detection function.
In recent years, attention has been given to a display panel configured by mounting a contact sensing device, a so-called touch panel, on a display such as a liquid crystal display or the like, or integrating the touch panel and the display, thereby causing the display to display various button images and the like to enable information input, in place of ordinary mechanical buttons. The display panel having such a touch panel is allowed not to have an input device such as a keyboard, a mouse, or a keypad and therefore, there is a growing trend to use the display panel in a portable information terminal such as a portable telephone, in addition to a computer.
There are types of touch panels including an optical type, a resistive type, and a capacitance type. For example, Japanese Unexamined Patent Application Publication No. 2009-244958 has proposed a so-called in-cell type display panel with a touch detection function. According to this document, a common electrode for display originally provided in a display is used as one of a pair of touch sensor electrodes, and the other (a touch detection electrode) is disposed to intersect this common electrode, in a capacitance-type touch panel. Meanwhile, there have been proposed some display panels each provided with a touch detection function, of a so-called on-cell type, in which a touch panel is formed on a display surface of a display.
Incidentally, in a touch panel in general, a human body serves as an antenna for a noise caused by an inverter fluorescent lamp, AM wave, AC power, and the like (hereinafter referred to as a disturbance noise), and the noise might be transmitted to the touch panel, causing a malfunction. Some studies have been made to reduce an influence of such a disturbance noise. For example, a touch panel allowed to change the frequency of a drive signal used in touch detection operation has been suggested in Japanese Unexamined Patent Application Publication No. 2006-106853. When a disturbance noise is at a specific frequency, this touch panel attempts to improve an S/N ratio by changing the frequency of the drive signal.